Control of fuel feeding devices



CONTROL OF FUEL FEEDING DEVCES Filed Jan. 2, 1941 2 Sheets-Sheet l f|1511 f g5 l 'X E I3 3 6 lol INVENTOR j BYAlbr .ono\.14- L my d 22A/2.

ATTORNEY Aug. 3, 1943.

A. E. BAAK CONTROL OF FUEL FEED-ING DEVICES Filed Jan. 2, 1941 2Sheets-Sheet 2 LVI/ ATTORNEY Patented Aug. 3, 1943 UNITED STATESPA'IENT- OFFICE CONTROL F FUEL FEEDING DEVICES Albert E. Baak,Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a' corporation of Delaware Application January 2,1941, Serial No. 372,783

9 Claims.

This invention is concerned with the control of fuel feeding devices,principally stokers and is particularly directed to improvements inautomatic systems for controlling stokers in response to temperature andtime and to improvements in timing apparatus adapted for use in suchsystems.

It is common practice to control stokers by means of a space thermostatand a timing device,- the latter serving to intermittently operate thestoker for fire maintaining purposes during mild weather. The controlarrangement is usually electrical, comprising circuits controlled bycontact mechanism operated by the timing device and by the spacethermostat. l

The object of my invention is to provide an improved electrical systemfor controlling a stoker by a thermostat and a timer, the improvementsresiding in part in arrangements whereby control from the timer andadjustment of the timed operation are simplified so as to reduce thecost of manufacture and enable operators to adjust the controls withgreater facility.

Another object of my invention is to provide an improved arrangement forcontrolling a relay by means of a timer wherein the contacts which causeenergizaton of the relay need not be snap acting and the length of theenergized period of therelay may be adjusted merely by adjusting ascrew.

Another object is to provide an improved heat actuated device forproducing rotary motion of a timing device. 1

Another object is to provide an improved heat motor for a timer havingan expansible and contractible heat responsive element andarrangementswhereby the element rotates a member about a sha-ft both when theelement cools and when it heats.

Another object is to provide a device as set forth in the foregoingobject wherein the heat motor is located within the rotary member.

Figure l is a partly diagrammatic view of a stoker control systemembodying my invention showing the details of the heat motor actuatedtimer.

Figure 2 is a plan view of the timer cam.

Figure 3 is a view of a completely assembled control unit, embodying thetiming mechanism," relay and transformers.

Figure 4 is a view of an unassembled part of the timing mechanism.

Figure 5 is a View similar to Figure 4 showing parts of the timingmechanism more completely assembled.

Figure 6 is a detail of the contacting mechanism, and

Figure '7 is a view of a modified form of heat motor.

Referring to Figure 1 of the drawings, numeral I 0 designates a stokerwhich may be of any known type and which forms part of a fuel burningdevice which may be any of various known forms. The controls for thestoker 1nclude a relay II having a winding I2, the armature of which isconnected to movable switch blades I3 and I4 having electrical contactsl5 and I6, the switch blades moving to the left when the winding I2 isenergized bringing their contacts into engagement with fixed electricalcontacts I1 and I8 respectively. Numeral 2l designates a spacethermostat of a known type comprising a circular bimetal element 22 towhich is attached two switch blades 23 and 24 movable to the left by thebimetal element into engagement with fixed electrical contacts 25 and 26respectively. The bimetal element 22 contracts upon a drop intemperature, its free end then moving in a direction to move the blades23 and 24 to the left, the blade 24 engaging contact 26 at apredetermined temperature which may be 72, for example, and the blade 23engaging the contact 25 at a, predetermined lower temperature which maybe one or two degrees lower, for example, this lower temperature may be70. Power for operation of the relay II is supplied by a stepdowntransformer 29 having a primary winding 30 and a secondary Winding 3 I,the primary winding having a greater I number of turns than thesecondary winding.

- Power is supplied to the transformer 29 through wires 32 and 33 whichmay be connected to any suitable power source.

The relay II may also be controlled by a time operated contactingmechanism which is designated generally by the numeral 35; the detailsof the time mechanism will presently be described. In connecton with thetiming mechanism 35, there is provided a second transformer 36 having aprimary winding 31 and a secondary winding 38, the primary windinghaving the greater number of turns. Numerals 39 and 4U designate lineconductors whereby power is supplied to the stoker and to thetransformer 36. The circuits ofthe stoker and the transformer 36 willpresently be described,

My invention contemplates the manufacture of designates the casing ofthe control unit or device. The transformers 29 and 36 are shownsuitably mounted on a panel 43 within the casing 42, which panel hasbrackets 44 and 45 which are i disposed between suitable ears on a -sidewall of the casing 42 and which are fastened nto the side wall of thecasing 42 by bolts as shown. The

. relay I I of Figure 1 may be of the hinge type, as

shown in Figure 3, and is also mounted on the panel 43 on the side ofthe casing 42 opposite the transformers. In this type of relay the twopairs need not be described in further detail. At the upper part of thecasing 42, as seen in Figure 3, adjacent the opposite sides are bracketmembers 46 and 41 which are secured to the bottom of the casing andwhich have openings through which electrical leads may be carried to theinterior of the casing. Numeral 48 designates a terminal panel having abracket 49 which is secured to the bottom of the casing 42, as shown,for holding the panel 48in place. The panel 48 has a number ofelectrical terminals, as shown, formed by screws whereby the necessarywining connections can be made. Between the transformers and the relayis mounted a generally rectangular casing 50 which houses the timingunit or mechanism of Figure 1. The casing 59 has 'anges 5| and 52 whichare secured to the panel 43 by screws 53 and 54. Certain adjustments forthe timing mechanism are provided which may be made from the outside ofthe casing 56, and these adjustments will presently be described.

Referring back to Figure 1, the timing mechanism comprises a cylindricalmember 51 having substantial depth, -as shown, and the upper 'face ofwhich is constructed so as to form a cam. The member 51 has a portion 58at the upper part which is of smaller diameter, and it is carried on ashaft 59 which protrude's through the casing 50, as shown in Figures land 3. The upper face of the member 51 has four dwells 62, 63, 64 and65, as may be best'seen on the plan view of the cam member 51 shown inFigure 2. The dwells 62 and 64 are diametrically opposed, andthesedwells are of the same radial and angular extent.

'I'hey are spaced from the yperiphery of the member 51. The dwells havea gradual rise from the face of the member 51, and they have abruptvdrop-offs at 61 'and 68. At the drop-offs 61 and 68 there are smalldepressions in the face of the cam, 69 Aand 19 respectively, which areofrelatively small angular extent. The dwells 63 and 65 are diametricallyopposed and Ialso vhave a gradual rise with abrupt drop-oils at 1I and12. The dwells 63 and 65 are similar except that the dwell 63 is ofslightly greater radial extent than the dwells 62 and 64, and the dwell65 is of slightly greater radial extent than the dwell 63, and the dwell65 extending all the way to the periphery of the member 51. At thedrop-oils 1i and 12 are depressions 13 and 14 respectively in the faceof the member 51, these depressions being of the same radial extent asthe dwells 63 and 65 and being of Arelatively 'short angularextent.

From the foregoing, it will be understood that the cam member 5 1 iswholly within the casing 58 (which is shown more or lessdiagrammatically in Figure l) with the shaft 59 protruding from,

the casing 50 so that it may be manually rotated, 75

the shaft 59 having the deslgnationmanua adjacent it on the casing 50 asshown in-Figure'.

The cam member 51 is normally rotated ina counter-clockwise direction bya heat actuated device or heat motor designated generally at 11, whichheat motor is mounted on a panel 18. The panel 18 has the samedimensions las the casing 50 including its flanges, and the panel'18is'positioned between the iianges 5l and 52 `and the panel 43 with thescrews 53 and 54 securing the parts inassembled relationship, the' heatmotor 11, as will now appear, is inside of the cam member 51 which ofcourse, as has been pointed out above, is within the casing 50. 'i y gReferring now to the heat motor 11, numeral 19 designates an arborcarried onv the panel. 18 and rotatably mounted on the arbor 19 isamember having a downwardly extending arm 8| and an upwardly extendingarm 82. Numeral 8f3 designates a normally xed arm member pivotallycarried on the arbor 19 but having ascrew 83a attached thereto whichextends through an arcuate slot 84 in the panel 18 which screwcarspiralisthen coiled into a second spiral as shown.

This arrangement of the bimetal makes il'rpossi'- ble to have arelatively large amount of bimetal arranged in a small and compactspace, the amount of bimetal being suicient to provide a relativelylarge amount of movement when the bimetal expands and contracts inresponse to temperature changes. This particular arrangement of bimetalexpands and contracts in. re-

spense to temperature changes along a straight line in the direction ofits axis. v At the end of arm 82 is attached a nger 81 which engageslthe interior of the skirtl formed by the cam member 51, the interiorsurface of the skirt being grooved or serrated as shown in Figf ure 1.Numeral 88 designates an angular-arm pivoted on a xed pivot 89 and alsopivoted to'an ear on the member 86 by means of a pivot 98. At

the end ofA the arm 88 is a linger 9| similar to the` finger- 81 vwhichalso forms a pawl engagingthe interior grooved surface of the skirt,formedfby .the member 51. Numeral A designates a flexible Iblade, thelowerend of which is attachedv to ,the member 82 and the upper end ofwhich carriesl a contact 96, the upper end being slightlyA spaced fromthe arm 82. Attached to the upper'endo'f blade 95 is an angular member91 which extends through an opening in arm 82 and which-has'a downwardlyextending projection adapted toengage the arm 82 and limit the extent towhich the blade 95 may be iiexed away from the arm- 82. Numeral 98designates a contact carried at the end of a contact screw 99 whichextends through a bracket member |00 which isfsuita'bly secured to thepanel v18. The contact screw 99 is disposed between .the legs of apermanent magnet Ii which is attached to the bracket |00 by means of aclamp |62 and a screw |03. The member 91.

forms an armature, and when it is broughttoa position adjacent the legsof the magnet IOI it is attracted by the iield of the magnet and thecontacts 96 and 98 are brought together, with a tion shown in Figure 1,the element 86 is cold and is therefore in its contracted position withthe legs 82 and 88 spaced relatively far apart, the contacts 96 and 98just having been snapped into engagement. Engagement of the contactscompletes a circuit for transformer 36 as follows: from line conductor39, through wire |01, primary 31 of transformer 36, Wire |08, arm 8|,member 80, blade 95, contacts 96 and 98, bracket |00, and wire |08 backto line conductor 40. Completion rotates the angular arm 88 in aclockwise direction about its pivot 89 so that this arm moves towardsthearm .82 with the pawf 9| sliding over the serrations on the innersurface of the skirt of member 51. The contacts 96and 98 stay inengagement with each other until the arm 82 engages the downwardlyextending projection of member 91, and when this occurs, furtherleftward movement of arm 82 pulls the flexible blade 95v to the left soas to disengage the contacts 9,6 and 98 interrupting the circuit oftransformer 36. When the circuit of transformer'36 is thus interrupted,winding 38 is deenergized and heating of element 86 discontinues and itbegins to cool and contract. Member 80 is now rotated in a clockwisedirection and angular arm 88 is now rotated in a counter-clockwisedirection, the arms 82 and 88 moving away from each other. Pawl 9| nowengages the serrations on the inner surface of member 51 rotating itagain in a counter-clockwise direction and pawl 81 slides over theserrations. The arms 82 and 88 continue moving away from each otheruntil contact 96is snapped into engagement with contact 98 with theparts again in the position shown in Figure l wherein the circuit oftransformer 36 is completed. It is to be noted that flexible blade 95provides some freedom of relative movement between arm 82` and contact96, that is, lost motion, so that considerable movement of arm 82 isrequired to effect opening and closing of contacts 96 and 98. By reasonof the flexible blade 95, arms 82 and 88 can move with a smooth back andforth motion inasmuch as they are free from the effect of thesnap'action with which contact 96 is operated.

From the foregoing, it is to be seen that the arms 88 and 82 alternatelymove toward and away from each other so as to walk around the innersurface of the member 51 so as to rotate it substantially uniformly andcontinuously in a counter-clockwise direction. By loosening the screwwhich extends through the slot 84, the position of arm 83 may beadjusted and such adjustment of course adjusts the position of element86 and the actuator arms 82 and 88. If arm 83 is adjusted to the right,it is to be Iseen that arm 82 is adjustedin a counter-clockwisedirection bringtacts. n the other hand, if arm 83 is adjusted length ofthe steps taken by the legs, 82 and 88 is adjusted by adjusting theposition of arm .l0 of this circuit energizes the transformer which 8 3.Thus by adjusting the positionof arm 83, the length of time required forthe member 51 to make one complete revolution may be adjusted.

Arm 83 is so adjusted that normally the memberA 51 makes one completerevolution per hour.

Within the casing is acam follower arrangement and a contactingmechanism operated thereby. The outer side of casing 50 forms anadjustment or control panel, and on the inner surface of Vthis side ofthe casing 50 is carried a plate to which is attached the cam follower.The control panel formed by the outer side of casing 50 may be best seenon Figure 3 and the mechanism carried o n the inner surface of thecasing 50 as may best be seen in Figure 1. Nu- -meral ||4 designates apin having a relatively large "head, the slot ||3 engaging the pin ||4so as to be guided thereby. At the end of each of legs and ||2 are threesmall spaced apertures, and cooperating with the apertures in each legare small bossesv ||5 and ||6 raised from the surface of the inner sideof'the control panel of casing 50. These bosses ||5 and 6 are adapted tofit into the apertures in the legs and ||2 of plate ||0 so as 4to holdthe plate I I0 in any one of three different positions. Numerals I|9designates a screw attached to the plate ||0 which extends through aslot |20 in thejcontrol panel of casing 50. There are indicia adjacentthe slot |20, as may be seen on Figure 3, the purpose of which will beexplained presently. The screw 9 may be manually grasped and moved up ordown in the slot |20, as seen on Figure 3, so as to movev the plate 0into any one of its three positions with the vbosses ||5 and |6 engagedin one of their associated apertures in the legs and ||2.

The plate v| I0 has two downwardly extending legs |22 and |23.Y At thelower end of lthese legs,

there are openings, and engaged in these openings are projections at theends of a V-shaped member |24 which forms the cam follower. Theengagement of the member |24 with the legs |22 and |23 permits pivotalmovement of the cam follower. The position of the cam follower withrespect to the cam in the casing 50 is best shown .in Figure ,1. The camfollower has an extending portion |25 lying, in the same plane, and thisportion has two projecting portions |26 and |21 lying in a perpendicularplane (see Figure 1).

cause arm 82 to engage the downwardly extending projection of member 91for opening the con- The projection |26 rides on the cam member 51. Theprojection |21 of the cam follower |24 nor- Vmally bears against anabutment |28 formed at opening in the side wall of the casing adjacent apair of ears |32 and |33 extending outwardly from the side of the casing50. The shoulders are pivoted to the ears by means of a, pin |34, asshown on Figures 3 and 5, whereby7V the member |29 may move pivotallyabout the'pin |34, that is in the manner of a hinge. |29 is normallybiased about its pivot away from the control panel of casingl 50 by acoiled spring as may be seen on Figure 6. 'Ihe member |29 has a medialrib |35 and the abutmentl |28 forms part of a broader rib |36, therebeing rectangular recesses or depressions on opposite sides of rib |36.Numeral |31 (see Figure 6) designates a flexible contact blade, theright end of which is attached to the member |29 in the recess at oneside of rib |36. At its free end, blade |31 carries electrical contacts|39 and |39. The blade 31 has an ear |40 for attaching an electricallead thereto. Numeral |4| designates a U-shaped contact bracket which isattached to the member |29 by rivets or the like as may be best seen onFigure 5. The member |4I` has a leg |42 which is flexible, the entirebracket |4| being made of flexible material. At its end the leg |42carries a contact |43 which is adjacent and cooperable with the contact39. The member |4 has a leg |48 which carries a contact |44 at its endwhich is hidden by the cam follower on Figure but which may be seen onFigure 1. The contact |44 cooperates with a contact |45 on the end of acontact screw |46 (see Figure 1) which -is carried at the end of acontact bracket |41 which is suitably secured to a side of the casing50. There are rigid backing members interposed between each of the legs|42 and |48 and the member |29, and one of these may be seen at |50 onFigure 6. The member |4| has an ear |5| for attaching an electrical leadthereto.

The contact |39 at the end of blade 31 cooperates with a contact |53(see Figures 1 and 6) carried at the end of a contact bracket 54 whichis suitably secured to a side of the casingl 50. Numeral .|55 designatesa rotatable member Member which is rotatable by a screw |56 whichextends through the control panel of casing and which is rotatable fromoutside of the casing. The memberv comprises a disk portion |51, part ofwhich is of slightly greater radius than the other part wherebyshoulders are formed, as seen on Figure 4, and these shoulders cooperatewith a stop |56 so as to limit rotation of the member.` |55 by the screw|56. The portion |51 has numbered graduations on its face from 2 to '7and these graduations are visible through a-slot |60 in the controlpanel of casing 50.. As will be explained hereinafter the screw |56 isan adjustment for adjusting the length of time that the stoker isautomatically operated by the timing mechanism for purposes ,ofmaintaining the re. The member |55 hasv a circular rib |6|, the edge rof which forms a gradually rising surface, the rib |6| forming a camwhich bears against a' shoulder |62 on the contact bracket |54; thus byrotating the member 55 by means of the screw |56, the rib |6| moves thebracket |54 so as to adjust the position of contact |53. By thusadjusting the position of contact |53, the period of time that .contacts|53 and |38 are kept engaged is varied, pas will presently be described.

Reference is now made particularly to Figure 1 wherein the relativepositions of the cam, the cam follower and the contacting mechanismwithin the casing 50 are shown. Theprojection |26 of the cam follower|24 rides on the cam 51 adjacent its periphery, and as the cam rotates,

one or more of the dwells on the cam lift the left end 0f the camvfollower |24 rotating it slightly causing the projection |21 which bearsagainst abutment |28 to move the member |29 in a counter-clockwisedirection, as seen on Figure 6. that is to move the contacts |43 and |44upwardly, as seen on Figure 1. When the screw ||9 is moved downwardly inslot |20 to the end of the slot (this would be leftward movement ofscrew |9 as seen on Figure 1), the end of the cam follower |24 andprojection |26 are very close to the edge of cam 51 so that under thecircumstances the prois, there is then only one contacting operation andconsequently only one timed operation of the stoker per hour as willpresently appear, lthe screw ||9 being adjacent the graduation marked 60(the graduations adjacent slot |20 indicating minutes of time) on thecontrol panel of casing 50. When the screw ||9 is movedto a mid positionin slot |20, the cam follower has its left end moved toward the centerof the cam sufficiently so that projection |26 will miss the dwells 62and 64 but both of the dwells .63 and 65 will be effective. There willnow be two contacting operations per hour produced by the timingmechanism, the screw I|9 being adjacent the graduation vmarked 30 on thecontrol panel of casing 50. When the screw ||9 is moved to the upper endof the slot |20, as seen in Figure 3, that is to the right as seen inFigure 1, the left end of cam follower |24 is moved towards the centerof the cam sufdciently so that the projection |26 will now not miss anyof the dwellsand consequently there will be four contacting operationsper hour, the screw ||9 now being adjacent the graduation marked |5 onthe control panel of casing 50.

The contacts |44 and |45 are normally in engagement, and when the end ofthe cam follower is raised by one oi the gradually rising dwells causingthe end of member 29 to be lifted, the leg |48 exes, contacts |44 and|45 remaining in engagement, and contact |38 is brought into engagementwith contact |53. This will happen when the projection |26 is at apredetermined position on one of the gradually rising dwells,4

and as the end of member |29 continues to be lifted, upward movement ofleg |42 will move -"i contact |43 into engagement .with contact |39.

- now be described. Whenever the space temperature falls to '10 so as tobring both blades 23 and 24 into engagement with their associatedcontacts, the relay is energized through the following circuit: fromsecondary 3| of transformer 29 through wire |10, contact 26,'thermostatic blade 24, element 22, blade 23, contact 25, wire |1|, wire|12, contact bracket |4|; contacts |44 and |45, contact screw |46,contact bracket |41, wire |13, relay'winding I2 and wire |14 back tosecondary 3|. Energization of winding I2 causes blades |3 and |4 to moveto the left bringing their associated contacts into engagement.Engagement of contacts |5 and |1 produces a maintaining circuit for therelay II as follows: from secondary 3| of transformer 29 through Wire|10, contact 26, blade 24, element 22, wire |15, wire |16, blade |3,contacts I5 and l1, wire |11, wire |12, contact bracket |4|, contacts|44 and |45, contact screw |46, contact bracket |41, wire |13, WindingI2 and wire |14 back to secondary 3|. It will be seen that themaintaining circuit is independent of the therlmostatic contact 25 sothat after the relay has been energized, it will remain energized untilthe temperature rises to a value of '12 at which blade 24 disengagesfrom contact 26. It should be noted also that both the originalenergizing circuit and the maintaining circuit for relay extend throughthe contacts |44 and |45, which as pointed out above, are normallyclosed, and which I prefer to refer to as auxiliary contacts. When thecontacts I6 and I8 are engaged a circuit for the stoker l is completedas follows: from line conductor 39 to wire |80, through contacts |8 andI6, blade |4, wire |8|, through the stoker and wire |82 back to lineconductor 40. The stoker will be kept in operationv until thetemperature has risen to '12 so as to cause both of the thermostaticcontacts to be disengaged.

The heat motor driven mechanism operates continuously so as to keep thecam 51 constantly rotating in a counter-clockwise direction onerevolution per hour. When heat requirements are relatively low so thatthe thermostat does not often cause operation of the Stoker, the stokermust be intermittently operated by the timing mechanism to prevent thefire from going out. With the screw |9 in the mid position of slot |20as shown on Figure 3, the projection |26 at the end of the cam follower|24 is in such a position as to make the dwells 63 and 65 effective soas to produce two automatic timed operations of the stoker per hour.Thus when the end of the cam follower is raised by one of the dwells 63or 65, the end of member |29 will be raised and contacts |38 and |53will first be brought into engagement. these contacts are brought intoengagement, but when the end of member |29 is further raised andcontacts |39 and |43 are brought into env gagement, a circuit for therelay will be completed as follows: from secondary winding 3|,-

through wire |84, contact bracket |54, contacts |53 and |38, blade |31,contacts |39 and |43, contact bracket |4|, contacts |44 and |45, contactt screw |46, contact bracket |41, wire 13, winding |2 and wire |14 backto secondary 3|. The relay will now be energized and engagement ofcontacts I and |1 will complete a maintaining circuit for the relay asfollows: from secondary winding 3 I, through wire |84, contact bracket54, contacts |53 and |38, blade |31, ear |40, wire |81, Wire |16, bladeI3, contacts I5 and |1, Wire |11, wire |12, contact bracket |4I,contacts |44 and |45, contact screw |46, contact bracket |41, wire |13,winding |2 and wire |14 back to transformer secondary 3|. It will beseen from the immediately foregoing, that the maintaining circuit isindependent of the contacts |39 and |43. From the description previouslymade, it will be remembered that when the left end of member |29 israised, contacts |53 and-|38 are first brought into engagement but therelay is not energized until contacts |43 and |39 are brought intoengagement. `Thus as soon as the relay is ener- No circuits will becompleted when gized, a maintaining circuit is formed through contacts|53 and |38 which will be relatively firmly engaged at the time, andthis circuit is independent of the contacts |43 and |39 which at thetime are not yet firmly engaged inasmuch as the projection |26 risesonly gradually on the gradually rising cam dwells. By reasonof themaintaining circuit through the firmly closed contacts, sparking isprevented at the other contacts which are not immediately firmly engagedwhen the relay is energized. This contacting arrangement for eliminatingsparking and conse- 'quent deterioration of the contacts is a. featureof my invention. f

After the relay has been energized by the timing mechanism, the stokeris operated in the same manner as previously described. When the relay*has been so energized, it remains energized until the projection |26drops off the cam dwell which lifted it for operating the contactingmechanism. All of the timer contacts remain in engagement until theprojection |26 drops off the cam dwell. For instance, if the camfollower was lifted by the dwell 65, when the cam has rotatedsuiliciently, the projection |26 will drop in to the depression 14 foropening the contacts and deenergizing the relay as will presently bedescribed. As has previously been pointed out, the relay will beenergized when the projection |26 is at a predetermined position on oneof the cam dwells, for instance, on dwell 65, and this position will bedetermined by the adjustment of the contact bracket |54 as determined bythe position of member |51. After the relay has been so energized, apredetermined number of minutes will expire during which the cam 51 willcontinue rotating until the cam follower, that is projection |26, dropsin to a depression, for instance the depression 14. The parts are soarranged and adjusted that the said number of minutes will be the numberappearing through the slot of the control panel of casing 50 oppositethe index marker. In other words, the number of minutes during which therelay is kept energized by the timing mechanism is determined by theadjustment of screw |56, and the desired number of minutes can be setopposite the index marker on the control panel and visible through theslot |60.

When the projection |26 drops oi the drop-off of dwell into thedepression 14, the end of member |29 is allowed to move downwardly to aposition lower than normal inasmuch as the depression 14 is lower thanthe normal atface of member 51. When the end of member |29 is allowed tomove to the lower than normal position, the bracket |4| is moveddownwardly enough to cause contacts |53 and |38 to disengage, to causecontacts |39 and |43 to disengage and also to cause disengagement of thenormally closed auxiliary contacts |44 and |45. The contacts |44 and |45remain open only.for a very short time While the projection |26 is inthe depression 14 (or in a similar depression). As soon as the cam hasrotated sufficiently to bring the projection I 26 back up on the normalat face of the cam, the contacting mechanism is returned toits normalposition as seen in Figure l, wherein the auxiliary contacts |44 and |45are closed. The purpose of opening the auxiliary contacts `after eachtimed operation of the stoker is to pretimed operation, blade 24 of thethermostat 2| may be in engagement with contact 26, and while thisposition of the thermostat is not onecalling for stoker operation, ifthe relay has been energized, the thermostatic maintaining circuitthrough contact 26 would keep the relay in energized position unlessthis maintaining circuit were interrupted by disengaging contactsl44-and |45. Thus after there has been a timed operation of the stoker,the relay will be positively deenergized and will only be reenergized bythe thermostat if both blades of the thermostat are engaging theirassociated contacts. If during a timed operation of the Stoker the spacetemperature should fall sufficiently to cause both therlmostatic bladesto engage their associated contacts, at the endof the timed operationthe relay will be deenergized as described but will be reenergized inresponse to the normal thermostatic demand as soon as the projection |26of the cam follower has passed the depression at the dropoff of thedwell to reclose the auxiliary contacts.

From the foregoing, it should now be recognized by those skilled in theart that I have provided a very compact, inexpensive and Aeiiicientcontrol instrument embodying a timing unit occupying a minimum'of spacebut still offering great facility, ease and simplicity of adjustment ofthe timing operation. The timing unit itself `is driven by a heat motorwhich may be very cheaply made but which still provides a suitablerangev of adjustment ofthe timing and which produces uniform andaccurate timing operation.y

a nature .that they may all be made from a single small panel lying in asingle plane, the cam shaft also being so positioned that it may bemanually rotated by grasping its end lwhich extends through the controlpanel as described. The memberV 51y ofcourse is freely rotatable in avcounterclockwise direction, there being nothing to restrain itsrotation in this manner.Y 'I'he manifold advantages and utility of myinvention shouldbe apparent to'those skilled in the art from theforegoing.v

-.Referring to Figure 7 of the drawings, I have shownV a slightlymodified form of heat motor for driving the timing mechanism. In Figure7, the

l* .heat `motor is mounted on a panel 18j, the same asin Figure 1,andthe rotary member 51 is the same as that of Figure 1. In the presentembodiment, there are two bimetal elements 200 and 20| which are rigidlymounted in the position shown, being attached to brackets 202 and 203respectively. The heating element 204 which l is preferably insulated iscarried on the bimetal element 200 and one end of the heating element isconnected to the element 200 while the other end is connected to thesource of power.v At its.

,'upper end the element 200 carries an arm or finger 205 which forms a,pawl engaging the serrations on the innerv surfacel of the skirt ofmember 51. At its upper end, the element 20| carriesa similar nger206forming a pawl also engaging the-inner surface of member 51. Numeral 2011designates a contact carried at the upper end of element 200, andnumeral 208 designates a contact carried at the upper end of element I.When the heating element 204 is energized to heat the bimetal elements,the element 200 warps to the left and the element 20| warps to theright. When the elements cool, they Warp toward each other so as tobring the `contacts 201 and 208 together. v With the parts in theposition shown, the heating element 204 has been deenergized so vas toallow the elements 200 and 20| to cool so that they have warped towardeach other bringing the contacts 201 and 208 together. A circuit for theheating element 204 is now completed throughV 7 the heating element, thebimetai. element 20o,

contacts 201 and 208, the bimetal element 20| and the bracket 203, whichis also connected to the source of power. The heating element 204 beinginsulated, as long as it is energized its temperature rises .as the heattherein accumulates.v

The heat causes the bimetal elements 200 and 20| to warp away from eachother, element 200 -the heater during the time it is energized causesthe bimetal elements to continue to warp to some extent after thecontacts are opened. When the accumulated heat has been suflicientlydissipated so as to permit the bimetal elements to begin to cool, theywarp toward each other with the pawl 206 now rotating the member 51 in acounter-clockwise direction and the pawl 205 sliding over theserrations. When the bimetal elements 'have cooled sufliciently, theparts again assume the position shown in Figure 7 and the cycle isrepeated. It is to be seen therefore that the arms or pawls 205 and 206walk around the inner surface of member 51 similarly to the operation ofthe previous embodiment.

The forms of my invention which I have disthe art which fall Within thespirit and scope of l the invention. 'Ihe invention therefore is to belimited not by my disclosure but only by the claims appended hereto.

I claim as my invention;- 1. In apparatus of the character described,.in

- combination, an automatic stoker, control means for the stokercomprising a relay, means controlling the relay comprising contactingmechanism, a timing device capable of producing uniform cyclingoperation of the contacting mechanism, said timing device comprising arotatable element, means forming a cam having gradually rising dwells, acam follower associated with said cam, said mechanism having two pairsof electrical contacts operated by said follower so arranged that thetwo pairs of contacts are engaged sequentially as the follower rises ona dwell, circuit means whereby the last to close of said pairs ofcontacts energizes said relay and whereby a maintaining circuit for saidrelay is formed through the `other pair of contacts, manual means foradjusting at least one of said contacts for varying the position of thecam follower with respect to a; dwell at which the con-' tacts close toenergize the relay and to thereby vary the period of time the relay isenergized, actuating means for uniformly rotating the said rotaryelement comprising an arm having a. pawl adapted to engage the element,a. second arm having a pawl adapted to vengage said element,

heat responsive means for actuating said arms,

means whereby said heat responsive means a1- ternately heats and coolsso as to cause it to expand and contract, and means whereby said heatresponsive means actuates said arms so as to cause one pawl to move theelement in a given direction when the heat responsive means expands andto cause the other pawlto move the as the follower rises on a dwell,manual means for adjusting one of said contacts whereby the point on adwell at which at least one pair of contacts closes may be varied, arelay controlled by said contacts, circuit means whereby the last toclose of said pairs of contacts energizes said relay and whereby amaintaining circuit for the relay is formed through the other pair ofsaid contacts, means including a thermostat ofthe type having two pairsof contacts which close in sequence for controlling said relay, circuitmeans whereby a maintaining circuit for said relay may be formed throughthe first to close of said lpairs of contacts of the thermostat, meansincludving an additional pair of contacts actuatable by said cam, saidlastpair of contacts being nor- `mally closed and connected in circuitwith said relay and said cam having a contour such that said last meansopens said additional contacts for a relatively short interval of timewhen said follower is at a position on the cam to deenergize the relay,opening4 of said additional contacts interrupting the maintainingcircuit of said thermostat.

3. In apparatus of the character described, in combination, meansforming a circular cam having gradually rising dwells which rise fromthe normal surface of the cam, said dwells having abrupt drop-offs, andsaid cam having' depressions in its normal surface of relatively smallcircumferential extent at the drop-offs, cam follower means associatedwith the cam, means .forming electrical contacts operated by said camfollower means, a relay and circuit means whereby the relay may beenergized by said contacts,

the arrangement being such that the contacts close when the cam followermeans are on a dwell and open when the cam follower means drop off adwell, and additional normally closed contact means operated by said camfollower means for interrupting the relay circuit when the cam followermeans drops into one of said depressions.

4. In apparatus of the character described, in combination, meanscomprising an automatic stoker, means for controlling ,the stokerincluding a relay, timing mechanism for controlling the relay comprisingmeans forming a circular cam having gradually rising dwells which risefrom the normal surface of the cam, said dwells having abrupt drop-offs,and said cam having depressions in its normal surface of relativelysmall circumferential extent at the drop-offs, cam follower meansassociated with the cam, means forming electrical contacts operated bysaid cam follower means, circuit means whereby the relay may beenergized by said contacts, the arrangement being such that the contactsclose when the cam follower means are on a dwell and open when the camfollower means drop off a dwell, means comprising a space thermostatofthe type having two pairs of contacts which close sequentially, andcircuit means whereby the thermostat may also control the relay, therelay being adapted to form a maintaining circuit for itself through thefirst to close of the thermostatic contacts when the relay is energized,and additional normally closed contact means operated by said camfollower means for interrupting the relay circuits when the cam followermeans drops into one of said depressions, said last mentioned contactmeans preventing the relay from remaining energized through thethermostatic maintaining circuit after the relay has been initiallyenergized by the timing mechanism.

5. In apparatus of the character described, in combination, an automaticstoker, control means for the Stoker comprising a relay, meanscontro-lling the relay comprising contacting mechanism, a timing devicecapable of producing uniform cycling operation of the contactingmechanism, said timing device comprising a rotatable element, actuatingmeans for the element located therewithin comprising an arm having apawl adapted to engage said element, a second arm having a pawl adaptedto engage said element, heat responsive means for actuating said arms,means whereby said heat responsive means alternately heats and cools soas to cause it to expand and contract, and means whereby said heatresponsive means actuates said arms so as to cause one pawl to move theelement in a given direction when the heat responsive means expands andto cause the other pawl to move the element in said given direction whenthe heat responsive means contracts, said timing device comprising meansforming a circular cam having gradually rising dwells which rise fromthe normal surface of the cam, said dwells having abrupt drop-offs, andsaid cam having depressions in its normal surface of relatively smallcircumferential extent at the drop-offs, cam follower means associatedwith the cam, means forming electrical contacts "operated by said camfollower means, circuit means whereby said relay is controlled by saidelectrical contacts, the arrangement being such that the contacts closewhen the cam follower means are on a dwell and open when the camfollower means `drops off a dwell,

means comprising a space thermostat of the type having two pairs ofelectrical contacts which close in sequence, circuit means whereby thethermostat also controls the relay, the relay being adapted to form a.maintaining circuit for itself extending through the first to close ofsaid thermostatic contacts when the relay is energized, and additionalnormally closed contact means operated by said cam follower means forinterrupting the relayv circuit when the cam follower means drops intoone of said depressions, said last mentioned contact means operating toprevent the relay from remaining energized through 1 the thermostaticmaintaining circuitwhen thev initially energized by the` timinga asaaooaa l within lthe casing and having a plurality of cirv cularly arrangedcam surfaces of substantially element, actuating means for the elementlocated therewithin comprising an arm having a pawladapted to engagesaidelement, 'a'second element having a pawl adapted to engagel saidelement, heat responsive means for ac'tuatingsaidarm, means whereby saidheat responsive means alternately heats and cools so as to cause ittoexpand and contract, and means whereby said heat'responsive meansactuates said arm so as to cause one pawl to move the element in a givendirection when the heat responsive means expands and to cause the otherpawl to move the element in said given direction when the heatresponsive meansA contracts,said timing device" including means forminga circular camhaving gradually' rising dwells which rise fr om'thenorits normal surface of relatively small circunfferential extent at.the .drop-offs, cam4 follower means associated withthe cam, saidmechanism having-two pairs of electrical contacts operated by said camfollower so arranged that vthe two .mal surface of the cam, said dwellshaving abrupt f drop-offs, and saidcam having depressions in vuniformangular extent but of different radial width, a cam follower within saidcasing and engaging said cam, means for causing relative rotation ofsaid cam and cam follower, a switch comprising a pair of contacts one ofwhich is normally fixed and the other of which is associated with saidcam follower so as to be movable thereby into and out of engagement withthe normally fixed contact, means for moving said cam follower radiallyof said cam to vary the frequency with which said cam follower andmovable contact are actuated without varying the length of time thecontacts are engaged, and means extending outside of said casing foradjusting the spacing of said normally fixed contact with respect tosaid normally movable contact tovvary the length of time that saidcontacts are engaged.

8. In a timing switch, a casing, a circular cam within the casing andhaving a plurality of circularly arranged cam surfaces of substantiallyuniform 'angular extent but of diierent radial widtha cam followerwithin said casing and engaging said cam, means for causing relativerotation of said cam and cam follower, a switch asso-A ciated with saidcam follower and-movable there-- by into and out of contact makingposition, means pairs of contacts are engaged sequentially as thefollower rises on a dwell, circuit means whereby the last to close ofsaid pairs of contacts energizes said'relay and whereby a maintainingcircuit for s'aid relay is formed through the other pair of contacts,manual means for adjusting at `least one of said contacts for varyingthe position ofthe cam follower with respect to a dwell at which thecontacts close tov energize the relay and to thereby vary the period oftime the relay is energized, means including a space thermostat of thetype having two pairs of contacts which close in sequence and circuitmeans whereby the thermostat also controls the relay, said relay beingadapted to form a maintaining circuit through the first to close of thethermostatic contacts when the relay is energized, and additionalnormally closed contact means operated by said cam follower means forinterrupting the relay circuit when the cam follower means drops l' intoone of said depressions, said last mentioned contact means operating toprevent the relay from remaining energized through the'thermo. staticmaintaining circuit when the relay has been initially energized by thetiming device.

7. In a timing switch, a casing, a circular cam extending outside ofsaid casing for moving said cam follower radially of said cam to varythe frequency with which said cam follower and switch are actuatedwithout varying the-length of timethe switch is in its contact makingposition, and .further means extending outside of said casing to adjustthe movement'of said switch necessary to move it to contact makingposition thereby to vary the length of time that said switch is incontact making position when moved to that position by said camfollower.

9. In a timing switch, a casing, a v circular cam within the casing andhaving a plurality of circularly arranged cam surfaces of substantiallyuniform angular extent but of different radial width, a cam followerwithin said casing and engaging said cam, means for causing relativerotation of said cam and cam follower, a switch associated with said camfollower and movable thereby into and out of contact making position,means extending outside of said casing for movingsaidcam follower awayfrom and closer ,to

ALBERT E. BAAK.

